1. Field of the Invention
The present invention relates generally to a process for chemical waste disposal, and more particularly to a wet oxidation process for disposal of a chelate waste solution.
2. Description of the Related Art
Chelates are used in both fossil and nuclear steam generator chemical cleaning processes. Waste disposal from a fossil unit cleaning is normally sent off site for treatment and disposal. Nuclear cleaning wastes are generally slightly contaminated with radionuclides and as such require disposal at an approved nuclear waste disposal site.
Due to the high disposal costs at approved nuclear waste disposal sites, cleaning wastes are currently evaporated to less than 85% of the original volume. The resultant concentrate is then solidified and sent for burial. While this is sufficient for the present, it is anticipated in the near future that the disposal of chelates at approved nuclear waste sites will be discontinued. The chelates will have to be removed from the chemical cleaning waste prior to disposal.
U.S. Pat. No. 5,225,087 describes a recovery process of EDTA from steam generator cleaning solutions. U.S. Pat. No. 4,780,238 relates to natural chelating agents for radio nuclide decorporation. U.S. Pat. No. 4,681,705 describes a method of decontaminating mixtures of radioactively contaminated liquids. U.S. Pat. No. 4,587,043 also describes the decontamination of metal surfaces in nuclear power reactors. U.S. Pat. No. 4,880,595 relates to a process and apparatus for cleaning nuclear reactor cooling water. Other patents related to this subject matter include U.S. Pat. Nos. 5,115,036; 4,578,162; and 4,629,570.
Traditional wet oxidation processes are very effective in the destruction of free chelates. A free chelate is defined as those chelates that have not formed a complex with a metal ion. In a chemical cleaning solution, the majority of the chelates are in the complex state. This makes the chelate difficult to destroy using the traditional wet oxidation methods.
Accordingly, there is a need for a process which allows the safe disposal of chelate. Preferably, the method would separate the chelate from the metal complex to a free state where it could then be treated with a wet oxidation method to achieve a destruction of the chelate to 99.9% or greater.